Electrical resistance element.



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nnennr n. rannsn, or nnrnorr, mcnrean, laceration no nosnrs iann'uraorunrne courses, or main MICHIGAN, a conronnrron or mcnrean.

ELECTRICAL RESISTANCE ELEMENT.

1% Drawing.

. Detroit, in the county of Wayne and State oi Michigan, have invented a new and useful improvement in Electrical Resistance Elements, of which the following is a specification;

My invention consists in a novel resistance element adapted for general use for which articles of the class are intended, and

more especially suited for use in heating apphances. For this purpose, it is well known that the principal re uirement is durability,

and the resistivity s ould be high enough to enable the requisite heat to be developed in the space .afi'orded in commercial appliances. The durability of a wire of a resistance element maintained at a high temperature by internally developed heat caused by the passage of an electric current depends upon a very large number of factors and can determined only by test In my Patent No. 811,859, wherein I describe a resistance element of nickel and chromium, and mention as desirable, nickel chromium alloys with the chromium in the percentages of 10 and 15, I also stated that iron was not suitable for my purpose, and in working with iron as a substitute for nickel in the proportions therein mentioned,

the iacts are as stated therein. 1 have since discovered, however, that there is fa somewhatsharp change in the durability of the allo when the chromium is used in hi h ercentages, as from 20pm" cent. upward, and

when 25 per cent. chromium is used,the 'alloy is extremely durable, althou h it is a trifle "less durahlethan the cross ingly resistant nickel chromium alloy therein described. However for asset low temperatures, say at 808 U, and particularly where the element is to he used in large quantities and price is a consideration, the iron chromiumcomposition is very desirable. it has a re- Specification of Letters recent. Application filed Sehtember 30,1912. Serial Ito. 723,194.

Patented Again. it, ieia.

sistivity of approximately 56 microhms per I centimeter cube, which is suficiently high for most uses. Y

The res1stance element of the composition.

above mentioned can, when suitable materials are used, be drawn into wire form as high as 35 per cent. chromium, as "far as I know now, but with the rapid advance at rolling methods, and the possibility of obtaining purer metals, much higher proportions may be drawn in the tutur Resistance elements containing from 20 to 35 per cent. chromium are generally uniform in character but with slightly greater life and slightly higher resistivity as-the chromium increases, and it is not to be anticipated that a further increase of chromium withi; any limits which may be found workable in the future, will materially change the properties. Manifestly, still greater proportions of chromium might be if cast grids or the like were used.

it will be understood, of course, that while I have described my invention in its preferred form accurately, I do not intend to limit myself thereto except as pointed out in the claim, and it will also be understood that various other materials he added to the resistance elements specified without materially injuring them. Manganese will ordinarily be used as a deoxidiserand the use of a slight excess slightly increases the resistivity without materially injuring the I element.

ALBERT n Manse. In presence of- I J. G. ANnnasoN,

J. 'LANDEBMAN. 

